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THE HISTORY A.ND, SHAPE OF THE -TEST-PIECE.
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who has given me the results obtained by him in testing boiler! plate. The steel ranged in strength from 55,400 to 61,300 pounds. per square inch, and was of nearly uniform chemical composition. The records are given in Table XVI-N.                           •
SBO. XVIj. — Influence of a change in length. — To determine the relative elongation with varying length, I carried out the following investigation: Twenty rods, three-quarter * inch in diameter, were, selected from one heat of acid open-hearth steel. From each rod. seven bars were cut, one of which was tested in a length _Qfv£, inches, and one each in 4, 6, 8, 10,. 12 and 14,-lnches,. The results, are given in Table XVI-0. The individual records of elongation are shown to prove that the aferagep are •not formed! by the combination; of unlike members. These clata" are plotted in Curve- AA, Fig. XVJE-A. :A similar series of tests was made by Barba,* the results
'        :                 •       TABLE'
;            i            '             ;   /      •
Influence of Changes in the 'Length. , •
&-lnch rounds; Pennsylvania Steel :Coinpany add! open-hearth rivet steel.
	v< •	Xiength of test-piece in inohej.						
:        |        ;          .   • •	^	Si	4	6	i'8	10	12	14
Ult. strength ; Ibs. per square inch.	Av.	60685	60343	60099	60128	60068	60059.	60060
Elastic limit ; Ibs. per square inch.	Av.	42548	43184	42951	43159	48161	43024	43284
Elastic ratio ; percent.	Av.	70.11	71.48	.71.47	71.78	71.85	71.64	71.98
Reduction of area ; per cent.	Av.	66.7	66.9	67.1	66.8'	«7.3	67.2	67.1
	•1	47.50	85.00	80.67	80.50	28.20	27.17	26.43
	.    2	46.00.	85.50	80.67	80.50	29.80,	27.67	26.48
	3	47.00	84.50	82.83	28.25	27.80	27.50	26.48
	4'	•48.50	85.50	82.00	80.25	28.20	25.00	27.00
	!5	47.00	85.50	83.00	28.75	29.00	27.17	28.14
	.6	46.50	89.00	82.67	28.75	81.60	29.83	28.21
	7	47.50	87,50	31.33	30.50	29.40	27.83	25.71
1                       '             .'         :'•	8	46iOO	88,00	80.00	80.00	26.60	28.00	24.43
	'9	47.50	85.50	84.33	81.75	80.40	29.88	28.21
	10	47.50	86.00	80.33	29.50	28.80	28.50	25.29
Elongation]; per cent.	11 12	49.00 49.00	84.75 86.50	80.00 81.33	31.00, 29.50	80.20 27.80	27.75 29.88	27.57 28.71
!     i •    ••••             '••'	18	47:00	35.50	32.83	29.00:	26.60'	27.00	26.43
i                            r	i!4	47.50	88.00	81.67	82.75	81.00	80.50	26.79
	15'	48.50	87.00	38.83	80.75	29.00	28.88	27.64
	16	47.50	'87.00	88.00	81.25	81.00'	27.75	29.29
	17	48.50	87.00	82.50	.29.00	28.20	27.88	27.21
,. ,      :.      '   ' .                .	• 18	46iOO	85.00	84.67	'28.75	28.00	28.75	25.80
	19	47.00	87.00	83.00	80.00	27.50	27.00	26.29
	20	47.50	87.50	34.83	82.50	80.00	26,25	28.14
	Av.	47.43	86.11	82,17	30,16-	28.96	27.87	26.761
,* Resistance des Maieriaux; Memoires de la Societe des Ingenieurs Qivils. Vol. 1, •p." 682.                      '                  ''"'"•                                •